I finished this book a week ago. Darling talks about how life started here on earth, the extreme places we've found life, and where and how we would find evidence of life elsewhere in the universe.

This is a decent book. Darling does a good job explaining the different components of life at a high level - i.e. you don't need a degree in biology to follow the text. He also covers a number of theories about abiogenesis and discusses just how tough microbes can be in space. The only downside of the book is that it's already getting dated. It was written in 2002, and in 8 years scientists have found a slew of extrasolar planets (we've even imaged a couple), not to mention other advances and discoveries we've made in science. If Darling would write a 2nd edition I'm sure some of the material would change a bit (though the general arguments would probably stay the same).

It's a good book, and while I don't think it's a "must-read", it's worth the time you put into it.